ARCHITECTS FROM LONDON Building Contracts
for House Extensions & Renovations
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Building Contracts – intro
Building Contracts
You have chosen your builder, agreed the price and are ready to start construction.
At this point, it can be tempting to rely on the quotation, a few emails and a handshake.
For a substantial extension or renovation, that is rarely enough.
A building contract records what has actually been agreed between you and the contractor. It sets out the work, price, payment arrangements, timescales and what happens if something changes during construction.
A good contract does not make a project complicated.
It makes expectations clearer before thousands of pounds are committed and work begins on your home.
At Tholos, we help make sure the project is properly defined before the building contract is put in place.
Building Contract
What Is a Building Contract?
A building contract is a legally binding agreement between the homeowner and the contractor carrying out the work.
It should identify the project and establish the terms under which it will be built.
Depending on the contract, this can include:
- the agreed scope of work
- the contract price
- start and completion dates
- payment arrangements
- responsibility for different parts of the project
- how changes are dealt with
- insurance requirements
- procedures for delays or disputes
The exact contract used should reflect the size and complexity of the project.
A £20,000 internal alteration does not necessarily need the same contractual structure as a major extension and full-house renovation.
Building Contract
Why Is the Builder's Quote Not Enough?
A detailed quotation is extremely useful.
But it normally focuses on what the builder is pricing, rather than setting out the full relationship between homeowner and contractor.
For example, a quotation might tell you that the project costs £120,000.
It may not clearly tell you:
- when payments become due
- what happens if the work is delayed
- how variations are approved
- what happens if materials increase in price
- who is responsible for particular items
- how defects are dealt with
- what happens if either party wants to end the contract
A building contract fills those gaps.
The quotation and drawings can then form part of the wider contractual information.
Building Contract
Put the Contract in Place Before Construction Starts
The best time to agree the rules of the project is before there is a problem.
Once work has started, both sides have much less room to resolve disagreements calmly.
A homeowner may believe something was obviously included.
The builder may believe it was clearly excluded.
Without a properly defined agreement, both can genuinely think they are right.
Before construction starts, the key elements should therefore be understood and recorded.
That includes the scope, price, programme and responsibilities of everyone involved.
Building Contract
The Contract Should Match the Tender
The building contract should reflect the project that was actually tendered and agreed.
If the preferred builder submitted a quotation based on a defined package of drawings and specifications, those documents should not suddenly disappear once the contract is signed.
They help establish exactly what the builder has agreed to construct.
The contract information may therefore include:
- architectural drawings
- technical drawings
- structural information
- specifications
- the accepted tender
- agreed clarifications
- schedules where relevant
This creates a clear link between the design, the builder’s price and the work carried out on site.
Building Contract
Agreeing the Contract Sum
The contract sum is the amount agreed for the work included within the contract.
Ideally, this should be based on a properly developed design and tender rather than an early estimate.
The clearer the project information, the easier it is to establish what that figure actually covers.
Before signing, any important exclusions, provisional sums or allowances should be understood.
For example:
Contract price: £105,000
might sound very clear.
But if £20,000 of that figure consists of provisional allowances that could change substantially, the final project cost is much less certain than the headline number suggests.
Building Contract
Payment Schedules
Most builders will not wait until the project is finished to be paid.
Payments are normally made in stages as construction progresses.
The contract should establish how and when those payments are calculated.
A payment structure might relate to:
- defined stages of construction
- the value of work completed
- agreed payment dates
- valuations during the project
The important thing is that both parties understand the system before work begins.
Large unexplained upfront payments should be approached carefully, particularly where they bear little relationship to materials ordered or work completed.
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Building Contract
Avoid Paying Too Far Ahead
Cash flow is important to a contractor, but homeowners also need protection.
Ideally, payments should broadly reflect the value of work completed and materials legitimately associated with the project.
If the builder has received significantly more money than the value of the work on site, the homeowner is exposed if something goes wrong.
A clear payment process helps maintain a reasonable balance.
It also reduces arguments about when money is due.
Building Contract
What Happens When the Design Changes?
Changes happen during building projects.
You might decide to upgrade the flooring.
An unexpected condition might be discovered behind an existing wall.
A technical issue may require a different construction detail.
These are usually dealt with as variations.
The contract should explain how variations are instructed, priced and approved.
A sensible process helps avoid one of the most common construction disputes:
“I thought that was included.”
Where possible, the cost and time implication of a change should be understood before the additional work is carried out.
Building Contract
Keep Variations in Writing
A conversation on site can feel perfectly clear at the time.
Three months later, memories can be surprisingly different.
Significant variations should therefore be recorded.
That might include:
- what is changing
- why it is changing
- the additional or reduced cost
- any effect on the programme
- confirmation that the change has been approved
This protects the homeowner and the contractor.
It also gives you a much clearer picture of how the original contract sum is changing throughout construction.
Building Contract
What About Unexpected Work?
Renovations and extensions to existing properties can reveal things nobody could reasonably see beforehand.
You might uncover damaged timber, unexpected drainage or previous construction that does not match the available information.
A building contract cannot magically remove that risk.
What it can do is establish a process for dealing with it.
Instead of the builder simply carrying out additional work and presenting a bill afterwards, the problem can be identified, assessed and agreed through the variation procedure.
Building Contract
Start and Completion Dates
For many homeowners, the programme is almost as important as the price.
You may need to arrange temporary accommodation, move furniture, organise childcare or coordinate work around other commitments.
The contract should therefore establish the intended start date and how completion is dealt with.
Construction programmes can change for legitimate reasons, including:
- exceptionally poor weather
- unforeseen site conditions
- approved variations
- delays to specialist materials
- circumstances outside the contractor's control
The contract provides a framework for understanding when an extension of time may be justified rather than leaving the completion date completely open-ended.
Building Contract
What Is Practical Completion?
Practical completion is the stage when the main construction work is substantially complete and the building can generally be used as intended.
That does not necessarily mean every tiny issue has disappeared.
There may still be minor defects or finishing items to address.
Practical completion is important because it can trigger several contractual consequences, such as:
- the homeowner taking possession of the completed work
- final payment stages
- the beginning of the defects period
- changes to certain responsibilities and insurance arrangements
The exact implications depend on the contract being used.
Building Contract
Snagging and Defects
Most building projects have minor issues that need attention towards the end.
A door may need adjusting.
A paint finish may require touching up.
A fitting may not operate correctly.
These are commonly dealt with through snagging and the defects process.
A suitable contract can provide a period during which defects attributable to the contractor’s work are identified and corrected.
This is different from deciding months later that you simply do not like a design choice that was correctly built.
Clear drawings and specifications help distinguish between genuine defects and changes of preference.
Building Contract
Who Supplies What?
This should be clear before work begins.
Homeowners sometimes choose to purchase certain products themselves, particularly kitchens, sanitaryware, lighting or specialist finishes.
That can work perfectly well, but responsibility needs to be understood.
For each item, it should be clear:
- who is ordering it
- who is paying for it
- who checks dimensions
- who is responsible for delivery
- who stores it
- who installs it
If a homeowner-supplied bath arrives damaged or the wrong size, the builder should not automatically be responsible for the resulting delay.
Likewise, if the builder has accepted responsibility for supply, that should be clear too.
Building Contract
Insurance and Responsibility
Construction work introduces risks.
The building contract should deal appropriately with insurance and responsibility for the works.
Depending on the project and contract, this may include contractor insurance, existing building insurance and public liability cover.
Homeowners should also speak to their own home insurer before substantial building work begins.
Some standard home insurance policies require notification when major extensions or renovations are being carried out.
Do not assume your existing policy automatically covers everything simply because you are still living in the property.
Building Contract
Building Contracts and Technical Drawings
The contract is only as clear as the project it refers to.
A beautifully written contract cannot compensate for a design that is still full of unanswered questions.
Technical drawings help define:
- what is being built
- dimensions
- construction methods
- materials
- key junctions
- structural relationships
They therefore form an important part of creating a clear contractual scope.
The better the project is defined before appointment, the less room there is for different interpretations later.
Building Contract
Structural Information Should Be Agreed Too
Structural elements can represent a significant part of the cost.
If steelwork, foundations or major structural alterations are still unresolved when the contract is signed, the agreed price may contain substantial assumptions.
That creates a straightforward risk:
The structural design changes, and so does the price.
Completing the main structural design before tender and contract helps reduce that uncertainty.
Building Contract
The Cheapest Contract Is Not the Goal
The objective is not to create a contract that pushes every possible risk onto the builder.
A contractor who is expected to accept unknown or unreasonable risks will usually respond in one of two ways:
They increase the price to cover them, or disputes appear later.
A good contract should create clarity and a reasonable allocation of responsibility.
Both sides should understand what they have agreed to.
That is healthier for the project than trying to “win” the contract before construction has even started.
Building Contract
What If There Is a Disagreement?
Most construction issues can be resolved through clear communication.
But the contract should still establish what happens when an agreement cannot be reached.
Formal dispute procedures vary depending on the contract.
The important point is that there is an agreed framework rather than both parties having to decide what the rules are after the disagreement has already happened.
Good records also matter.
Drawings, emails, variation approvals, payment records and site information can all become important if there is later uncertainty about what was agreed.
Building Contract
From Builder Selection to Construction
Choosing the contractor is not quite the end of the pre-construction process.
Before work begins, you should ideally have:
- a clearly defined scope
- an agreed contract sum
- the relevant drawings and specifications
- structural information
- agreed start and programme information
- payment arrangements
- an appropriate building contract
hat extra preparation can feel less exciting than watching the first wall come down.
It is also one of the best opportunities you have to reduce unnecessary problems later.
Building Contract
A Clearer Route Into Construction
Tholos helps homeowners prepare the project before the builder arrives on site.
That means developing the design, resolving technical and structural requirements, obtaining comparable builder quotations and making sure the agreed project is properly documented before construction begins.
The objective is not paperwork for the sake of paperwork.
It is to make sure everyone starts the build understanding the same project, the same price and the same responsibilities.
Client experience
"
Lorem ipsum dolor sit amet, consectetur adipiscing elit. We had a vision for our home but no idea how to realise it. Tholos Interiors took complete ownership of the project — every detail was considered, every decision explained. The result exceeded everything we had imagined.
– Lawrence Ipsum, Homeowner · London –
Frequently Asked Questions
Do I legally need a building contract?
A building agreement can exist even without a lengthy formal document, but for substantial residential construction it is strongly advisable to use an appropriate written contract that clearly records what has been agreed.
Is a builder’s quotation a contract?
An accepted quotation can create contractual obligations, but it may not address many important issues such as variations, delays, payment procedures and defects. A suitable formal building contract provides much greater clarity.
When should I sign the building contract?
Ideally after the design and tender have been sufficiently resolved and before the contractor begins construction.
Should the drawings form part of the contract?
Relevant agreed drawings, specifications and tender information will normally help define the work the contractor has been appointed to carry out.
How should I pay my builder?
The payment mechanism depends on the contract, but payments should normally follow an agreed process and relate sensibly to the progress and value of the work.
What happens if construction takes longer than expected?
The contract should explain how delays and extensions of time are handled and when the contractor may have a legitimate reason for moving the completion date.
If you have selected your builder, the next step is making sure the project you have agreed to build is clearly documented before work begins.
Tholos can help you move from design and tender into construction with a defined scope, coordinated information and a much clearer agreement between you and your contractor.
This article is part of a series created by our dynamic marketing team for informational purposes only. While we strive to review all content thoroughly, occasional oversights may occur, even after publication. Therefore, we cannot accept liability for any interpretations or use of the information provided. For the most up-to-date information or to report any discrepancies, please contact us at hello@tholos-architects.com.
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